Bushing for transformers and the like

ABSTRACT

A bushing for a transformer or the like comprising an insulating member having a bore therethrough and an opening adjacent one end thereof intersecting with the bore and including at least one substantially flat side wall portion. The insulating member has a shoulder between said bore and opening. A rigid conductor member extends through the bore and opening and has a pair of threaded ends extending exteriorly of the bore and opening. The conductor member has a flange for abutting engagement with the shoulder and a retainer in threaded engagement between one of the threaded ends thereof and the other end of the bushing urging the flange into engagement with the shoulder. The conductor member carries a pair of spaced seals sealably engaged between the conductor member and the bore and defining therein an isolated chamber.

United States Patent 1 1 1111 9 3 Farmer et a1. 1 1 0, 1197 3- {541BUSHING FOR TRANSFORMERS AND T1112 58,844 1/1932 Norway 174/152 R lLiKEinventors: Donald J. Farmer; Charles ,1.

Carlson, both of Pine Bluff, Ark; Peter W. Muschong, St. Louis, Mo.

Primary Examiner-Laramie E. Askin AztomeyStuart N. Senniger et a1.

A bushing for a transformer or the like comprising an insulating memberhaving a bore therethrough and an opening adjacent one end thereofintersecting with the bore and including at least one substantially flatside wall portion. The insulating member has a shoulder between saidbore and opening. A rigid conductor member extends through the bore andopening and has a pair of threaded ends extending exteriorly of the boreand opening. The conductor member has a flange for abutting engagementwith the shoulder and a retainer in threaded engagement between one ofthe threaded ends thereof and the other end of the bushing urging theflange into engagement with the shoulder. The conductor member carries apair of spaced seals sealably engaged between the conductor member andthe bore and defining therein an isolated chamber.

1111 Cilnirns, 5 Drawing Figures BUSHING FOR TRANSFORMERS AND THE LIKEBACKGROUND OF THE INVENTION This invention pertains generally tobushings and in particular to high voltage bushing assemblies fordistribution transformers and the like.

The many different types of terminals required by different distributiontransformer customers such as utilities, etc., pose an increasingstorage and inventory problem for transformer manufacturers. Even thoughthere may be a substantial inventory of a particular size and style ofdistribution transformer, none may have the particular type high voltagebushing terminal required by a particular customer on short notice.Changing just the terminal entails considerable difficulty and expenseinasmuch as the seal of the transformer must be broken when a terminalis removed from typical conventional style high voltage bushings. Thisrequires further processing in the plant to reseal the transformer underproper conditions to insure against incursion of moisture, etc., afterthe new terminals have been installed.

Moreover, in order to obtain and maintain electrical contact between theterminal and the porcelain high voltage bushings and thus avoid acorona-inducing high-stress air gap, a stainless steel spring wasgenerally required between said terminal and porcelain portion. This wasundesirable from an economic and assembly viewpoint. Also, differentthrough-conductor structures were required in typical conventionalbushing assemblies depending on the high voltage ratings of theparticular bushings.

SUMMARY OF THE INVENTION Among the several objects of the invention arethe provision of high voltage bushing assemblies for transformers andthe like which permit the convenient changing of the terminals theretowithout breaking the seal of the bushing or the need to destroy theintegrity of the transformer itself by having to gain access to theinterior; and the provision of bushings of the type described which havea simplified construction so as to avoid steel garter springs betweenthe terminal and the porcelain and which are useful for a wide varietyof high voltage ratings. Other objects and features will be in partapparent and in part pointed out hereinafter.

Briefly, the bushing of the present invention comprises an insulatingmember having a bore there through and an opening adjacent one endthereof with the bore and including at least one substantially flat wallportion. The insulating member has a shoulder between the bore and theopening. A rigid conductor members extends through the bore and openingand has a pair of threaded ends extending exteriorly of the bore andopening. The conductor member has a flange for abutting engagement withthe shoulder, and a retainer in threaded engagement between one of thethreaded ends thereof and the other end of the bushing urging the flangeinto engagement with the shoulder. The conductor member carries spacedseals sealably engaged between the conductor member and the bore anddefining therein an isolated chamber.

DESCRlP'lllON OF THE DRAWlNGS FlG. l is a sectional view illustrating ahigh voltage bushing adapted for mounting engagement with a transformerhousing portion and embodying the present invention;

H6. 2 is a top plan view of the bushing insulating member of FIG. ll;

P16. 3 is an enlarged fragmentary view talren from FIG. ll showing thesealing engagement of the bushing with the transformer housing portion;

H6. 4 is an enlarged fragmentary view of the upper portion of thebushing conductor showing the upper sealing and locking membersdisengaged from the bushing; and

HO. 5 is a sectional view talten along line 55 of H6. 4.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DESCRlP'llON OF A PREFERRED EMBODIMENT Referring now to the drawings andin particular to H6. l, a bushing assembly, indicated generally at l, isprovided with an insulating portion or member 2 of porcelain or ceramic,or other insulating material, and a plurality of annular fins or skirts3 are integrally formed on the upper or exterior portion 4 of saidinsulating member to increase its insulating capacity. The insulatingmember includes an abutment or depending flange 5 having an annulargroove ti therein in which is disposed an annular seal or gasket 7 ofconductive rubber or synthetic elastomer material or an asbestosmetalliccomposition such as sold under the trade designation Flexitallic. Theseal 7 is engaged about an opening 8 in a transformer tank or housingportion, such as a housing cover or lid 9, and the lower or interiorportion lid of the insulating member 2 which extends through the coveropening 8 interiorly of the transformer is generally in the form of atruncated cone. A peripheral groove ii is provided on the interiorportion 10 of the insulating member 2 having retaining or abutment meanstherein, such as a coil spring 12. An adjustable clamping ring l3 havinga plurality of adjusting screws 14 therein is received on saidinsulating member lower portion. Clamping ring i3) is abuttingly engagedwith the spring l2, and screws M- are adjusted into abutment with theinterior side of the housing cover 9 urging the seal 7 at the flange 5into sealing engagement with said housing cover about the opening 8therein. The insulating member 12 is also provided with interior andexterior end portions l5, lb and a bore or central opening H7 isprovided through said insulating member between the interior andexterior end portions. Referring now also to H6. 2, a cross-slot, groove01' opening 13 is provided in the exterior end lb of the insulatingmember 2 intersecting with the bore l7. An abutment or shoulder ll8a isdefined in the insulating member at the juncture of the slot with thebore between opposed generally parallel flat side wall portions 18b.

A conductive stud or solid rod member 1% extends coairially through theinsulating member bore 17 having opposed threaded connecting ends 2h, 2iextending from the bore adjacent to the interior and exterior endporiions 15, lb of the insulating member 2, and a flange 22 havingopposed generally parallel abutments or flat portions 22a thereon isintegrally formed with said stud member and received in the insulatingmember slot 18 with the flats 22a in rotation-preventing engagement withthe slot side wall portions 18a. A pair of identical annular resilientsealing members or grommets 23, 24 are sealably engaged between the studmember 19 and the insulating member bore 17 and define therewith anisolated chamber 25, and the seal 24 is carried in abutment with thestud member flange 22 while the seal 23 is spaced from the interior endportion 15 of the insulating member 2 by an annular spacer or sleevemember, such as the seal seating member 26, received on stud member 19.A retainer member, such as a flanged nut 27, is threadedly engaged withthe stud member connecting end 20 and is abuttingly engaged with theinterior end portion 15 of the insulating member 2 thereby placing thestud member 19 under a tensile force which urges the seal 24 and thestud member flange 22 downwardly into sealing engagement with the bore17 and displacement-preventing engagement with the slot abutment 18a ofthe insulating member 2, respectively. It should also be noted that theretainer member 27 also serves as a seat for the spacer 26 obviating thedisplacement thereof from the insulating member bore 17, and upon theassembly of the retainer 27 on the end 20, as previously mentioned, theretainer also urges the seal 23 into engagement with the bore 17.

A high voltage terminal member 28 of any of the many types well known inthe art is threadedly received on the stud member connecting end 21, andanother grommet 28a, identical to the grommets 23, 24, is compressed inslot 18 substantially filling it when terminal 28 is mounted. Aresilient conical or Belleville type washer or locking member 29 isreceived on stud member connecting end 21 being biased in lockingengagement between terminal member 28 and the exterior end portion ofinsulating member 2. The resilient force of the washer 29 urges theterminal 28 upwardly compensating for a predetermined amount ofexpansion in the length of the tensioned stud member 19 at increasedtemperatures. A transformer coil lead terminal 30 is secured to the studmember connecting end 20 and retained thereon against displacement by alocking member, such as the jam nuts 31. In the assembly of the grommets23 and 24 on the rod 19, a protective nipple or guide (not shown) isplaced over the threaded rod ends 20 to prevent grommet cutting by thethreaded end which might impair sealing integrity of the grommets.

As shown in FIG. 3, a conductive strap 32 may be connected between theFlexitallic" seal 7 and the metal clamping ring 13 and to the coilretaining spring 12 if necessary to obviate the generation of coronabetween the insulating member depending flange and the housing cover 9.

From the foregoing, it is apparent that the tensile force applied to thestud member 19 by the retainer member 27, which is between said studmember and insulating member interior end 15, urges the stud memberflange 22 into displacement preventing engagement with the shoulder orslot abutment 18a of the insulating member 2 thereby capturing orretaining said stud member against displacement from the bore 17 whenthe terminal 28 is disengaged from the stud member connecting end 21. Itis also apparent from the foregoing that the stud member 19 having theseals 23, 24

mounted thereon effects an economical, simplified unitary assembly whichis insertable into the bore 17 to define the isolated chamber 25. Thesealed chamber 25 preferably contains dry air or an inert transformergas where bushing l is utilized for relatively lower voltage service(e.g., below 9,434 volts) or transformer oil e.g., for service up tol6,340 volts) or oil and a solid dielectric medium if the bushing isutilized for relatively higher voltage (e.g., above 16,340 volts)service. Thus, the bushing 1 is a multi-purpose unit which serves tosimplify manufacturing and reduce the types of bushings for inventorypurposes. Moreover, the external terminal may be easily changed withoutany access to the interior of the transformer tank or breaking of theseal of the bushing or unit. Further, it is apparent that the size ofthe bore 17 is decreased which results in an increase in the strength ofbushing 1. lt should also be noted from the foregoing that the highvoltage terminal 28 is in direct contact with the insulating memberexterior end 16 via the washer 29 thereby obviating any air gap betweenthe terminal and the exterior end which might result in corona.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. A bushing for a transformer or the like comprising an insulatingmember having a bore therethrough, an opening in said insulating memberadjacent one end thereof intersecting with said bore and including atleast one substantially flat side wall portion, a shoulder on saidinsulating member between said bore and opening, a rigid conductormember extending through said bore and opening including a pair ofthreaded ends extending exteriorly of said bore and opening, a flange onsaid conductor member adjacent to one of the threaded ends thereof forabutting engagement with said shoulder, a retainer in threadedengagement between the other of said threaded ends and the other end ofsaid bushing urging said flange into engagement with said shoulder, anda pair of spaced seals on said conductor member sealably engaged betweensaid conductor member and said bore and defining therein an isolatedchamber.

2. A bushing according to claim 1, wherein said seals constituteindentical resilient grommets.

3. A bushing according to claim 1, wherein said flange also defines aseat engaged with one of said seals.

4. A bushing according to claim 3, comprising a sleeve about saidconductor member in said bore having one end in abutment with saidretainer and the other end defining another seat engaged with the otherof said seals.

5. A bushing according to claim 1, comprising a sleeve in said borehaving one end thereof abuttingly engaged with said retainer and theother end thereof in seating engagement with one of said seals, saidconductor member extending through said sleeve.

6. A bushing according to claim 1, comprising at least one flat portionon said flange in abutting engagement with said flat side wall portionof said opening to obviate rotation of said conductor member in saidbore.

7. A bushing according to claim 1, wherein said opening includes anotherflat side wall portion substantially parallel with and opposed to saidfirst-named flat side wall portion, and opposed abutments on said flangerespectively engaged with said first-named and other side walls toobviate rotation of said conductor member.

8. A bushing according to claim 1, comprising a terminal received onsaid one threaded end.

9. A bushing according to claim 8, comprising a metallic washerconnected in abutting engagement between said terminal and said one endof said insulating member.

10. A bushing according to claim 8, comprising a resilient substantiallyconical washer biased in abutting engagement between said terminal andsaid one end of said insulating member, the resiliency of said washercompensating for a predetermined amount of expansion in the length ofsaid conductor member.

11. in a transformer having a housing with an opening therein, a bushingassembly including a porcelain insulating member extending through saidopening and having portions extending interiorly and exteriorly of saidhousing, an annular flange integrally formed on said exterior portionand extending about said opening, an annular seal disposed in saidflange means for sealing engagement with said housing about saidopening, a mounting ring secured to said interior portion, adjustablemeans between said mounting ring and said housing about said opening forurging said seal into sealing engagement with said housing about saidopening, a bore in said insulating member extending between the endsthereof, an opening in one of said ends intersecting with said boreincluding opposed substantially parallel side wall portions on saidinsulating member, and a shoulder on said insulating member between saidopening and said bore, a solid conducting rod extending substantiallycoaxially through said bore and opening and having a pair of threadedend portions exteriorly of said bore adjacent to said ends of saidinsulating member, a flange integrally formed with said rod adjacent toone of said threaded end portions and extending substantially radiallythereof for engagement with said shoulder, a pair of opposed flats onsaid flange respectively engaged with said side wall portions to preventrotation of said rod, a threaded member threadedly engaged with theother of said threaded end portions and including a second flange inabutting engagement with the other of said ends of said insulatingmember, said first-named flange being urged into engagement with saidshoulder in response to the threaded engagement of said threaded memberwith said other threaded end portion, a pair of spaced grommets sealablyengaged between said rod and bore and defining therewith an isolatedchamber in said bore, one of said grommets being seated against saidfirst-named flange, a sleeve received on said rod within said bore andconnected in abutting engagement between said second flange and theother of said grommets defining a seat therefor, a terminal forreceiving a power lead threadedly connected with said one threaded endportion, a resilient conical washer received on said one threaded endportion and biased into abutting engagement between said terminal andsaid one end of said insulating member, said other threaded end portionalso defining a terminal for receiving a transformer coil lead, and athird grommet engaged between said first-namecl flange and said washersubstantially filling said opening, said third grommet being identicalto the other grommets.

1. A bushing for a transformer or the like comprising an insulatingmember having a bore therethrough, an opening in said insulating memberadjacent one end thereof intersecting with said bore and including atleast one substantially flat side wall portion, a shoulder on saidinsulating member between said bore and opening, a rigid conductormember extending through said bore and opening including a pair ofthreaded ends extending exteriorly of said bore and opening, a flange onsaid conductor member adjacent to one of the threaded ends thereof forabutting engagement with said shoulder, a retainer in threadedengagement between the other of said threaded ends and the other end ofsaid bushing urging said flange into engagement with said shoulder, anda pair of spaced seals on said conductor member sealably engaged betweensaid conductor member and said bore and defining therein an isolatedchamber.
 2. A bushing according to claim 1, wherein said sealsconstitute indentical resilient grommets.
 3. A bushing according toclaim 1, wherein said flange also defines a seat engaged with one ofsaid seals.
 4. A bushing according to claim 3, comprising a sleeve aboutsaid conductor member in said bore having one end in abutment with saidretainer and the other end defining another seat engaged with the otherof said seals.
 5. A bushing according to claim 1, comprising a sleeve insaid bore having one end thereof abuttingly engaged with said retainerand the other end thereof in seating engagement with one of said seals,said conductor member extending through said sleeve.
 6. A bushingaccording to claim 1, comprising at least one flat portion on saidflange in abutting engagement with said flat side wall portion of saidopening to obviate rotation of said conductor member in said bore.
 7. Abushing according to claim 1, wherein said opening includes another flatside wall portion substantially parallel with and opposed to saidfirst-named flat side wall portion, and opposed abutments on said flangerespectively engaged with said first-named and other side walls toobviate rotation of said conductor member.
 8. A bushing according toclaim 1, comprising a terminal received on said one threaded end.
 9. Abushing according to claim 8, comprising a metallic washer connected inabutting engagement between said terminal and said one end of saidinsulating member.
 10. A bushing according to claim 8, comprising aresilient substantially conical washer biased in abutting engagementbetween said terminal and said one end of said insulating member, theresiliency of said washer compensating for a predetermined amount ofexpansion in the length of said conductor member.
 11. In a transformerhaving a housing with an opening therein, a bushing assembly including aporcelain insulating member extending through said opening and havingportions extending interiorly and exteriorly of said housing, an annularflange integrally formed on said exterior portion and extending aboutsaid opening, an annular seal disposed in said flange means for sealingengagement with said housing about said opening, a mounting ring securEdto said interior portion, adjustable means between said mounting ringand said housing about said opening for urging said seal into sealingengagement with said housing about said opening, a bore in saidinsulating member extending between the ends thereof, an opening in oneof said ends intersecting with said bore including opposed substantiallyparallel side wall portions on said insulating member, and a shoulder onsaid insulating member between said opening and said bore, a solidconducting rod extending substantially coaxially through said bore andopening and having a pair of threaded end portions exteriorly of saidbore adjacent to said ends of said insulating member, a flangeintegrally formed with said rod adjacent to one of said threaded endportions and extending substantially radially thereof for engagementwith said shoulder, a pair of opposed flats on said flange respectivelyengaged with said side wall portions to prevent rotation of said rod, athreaded member threadedly engaged with the other of said threaded endportions and including a second flange in abutting engagement with theother of said ends of said insulating member, said first-named flangebeing urged into engagement with said shoulder in response to thethreaded engagement of said threaded member with said other threaded endportion, a pair of spaced grommets sealably engaged between said rod andbore and defining therewith an isolated chamber in said bore, one ofsaid grommets being seated against said first-named flange, a sleevereceived on said rod within said bore and connected in abuttingengagement between said second flange and the other of said grommetsdefining a seat therefor, a terminal for receiving a power leadthreadedly connected with said one threaded end portion, a resilientconical washer received on said one threaded end portion and biased intoabutting engagement between said terminal and said one end of saidinsulating member, said other threaded end portion also defining aterminal for receiving a transformer coil lead, and a third grommetengaged between said first-named flange and said washer substantiallyfilling said opening, said third grommet being identical to the othergrommets.